In addition, this invention relates to a mixing method for mixing a fluid flowing in a main direction of flow through a flow channel, whereby the flow of the fluid is thoroughly mixed by a leading edge eddy system.
Such mixing devices and mixing methods are used in industrial plants, power plants, chemical plants, roasting mills and similar plants to mix or blend the fluid flows occurring there. For example, for exhaust gas purification, the exhaust gases must be mixed to achieve a uniform utilization and effective operation of the cleaning facilities.
A mixing device development by the applicant in this regard is the so-called static mixer in which thin mixer disks are arranged so the flow can pass freely by them in a flow channel. The mixer disks are inclined at an acute angle, also referred to as the oncoming flow angle, with respect to the flow. Then a particularly stable leading edge eddy system develops on the back of these mixer disks facing away from the flow. This leading edge eddy system consists essentially of two contra-rotating eddies from the free front and side edges, where the flow passes freely by them toward the inside and widening conically in the main direction of flow. These eddy pairs in the form of bags are also referred to in aviation engineering as eddy drag; they are very powerful and create a good mixing effect within a short mixing zone downstream of the mixer disk, also known as eddy induction disks or baffles with the very low slope of the mixer disk with respect to the main direction of flow. Because of the especially acute oncoming flow angle of the mixer disk in comparison with other mixer devices, there is only an extremely slight increase in flow resistance. Therefore, the pressure drop in this mixing device is especially low in comparison with that of other known systems.
So-called transverse mixers are used in the flow channels of the aforementioned installations, where these channels are frequently very broad. These transverse mixers equalize the temperature distribution, the chemical composition in the exhaust gases and the dust distribution, e.g., the flue ash, based on the principle of action of the static mixer. With these transverse mixers, multiple eddy induction disks are arranged along a row axis in a mixer disk row. The row axis of this mixer disk row runs essentially across the main direction of flow.
To further improve the uniformity of the flow, the present applicant has already proposed mixers in which multiple mixer disk rows of this type are arranged one after the other in the direction of flow. The second row is a minimum distance from the first row of mixer disks, which depends on the eddy formation produced by the first row. The second mixer disk row is thus arranged behind the first row so that the mixing eddy of the second mixer disk row supplements and strengthens the eddies of the first mixer disk row.
If additional additives (e.g., ammonia or ammonia water in denitrification plants, so-called deNOx plants, SO3 in the case of electrostatic filters, lime in coal boilers and the like) are to be incorporated into the first fluid which is flowing through the flow channel and is also referred to as the primary fluid, then an admixture device is installed downstream from the transverse mixer(s). This admixing device conveys the material to be admixed, hereinafter referred to as the secondary fluid, directly into the eddy system, which entrains the substance and mixes it thoroughly with the main stream. The substance to be admixed may be gaseous, in the form of a mist (aerosol) or a pulverized solid. With the known admixture devices, these may be narrow injection grids having numerous nozzles with which the additives are admixed and finely distributed in the primary fluid. These nozzle grids are installed at a minimum distance in front of any mixers. The minimum distance is selected to be large enough so that secondary fluid sprayed in is evaporated as completely as possible in the hot primary fluid before reaching the mixer because otherwise corrosion and erosion phenomena will develop on the mixers. These known mixing devices have already been used successfully for a long time. Nevertheless against the background of the further increase in demands regarding the efficiency of industrial plants, there is a demand for mixing equipment with a further boost in efficiency.